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istio.io/content/docs/tasks/traffic-management/egress/index.md

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title description weight aliases keywords
Control Egress Traffic Describes how to configure Istio to route traffic from services in the mesh to external services. 40
/docs/tasks/egress.html
traffic-management
egress

By default, Istio-enabled services are unable to access URLs outside of the cluster because the pod uses iptables to transparently redirect all outbound traffic to the sidecar proxy, which only handles intra-cluster destinations. This task describes how to configure Istio to expose external services to Istio-enabled clients in three different ways:

  1. Configure a service entry.
  2. Bypass the Envoy proxy for a specific range of IPs.
  3. Configure the Envoy proxy to pass requests through to external services on ports that are not configured inside the mesh.

{{< boilerplate before-you-begin-egress >}}

Controlled access to external services

Using Istio ServiceEntry configurations, you can access any publicly accessible service from within your Istio cluster. This task shows you how to access an external HTTP service, httpbin.org, as well as an external HTTPS service, www.google.com.

Access an external HTTP service

  1. Create a ServiceEntry to allow access to an external HTTP service:

    {{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: networking.istio.io/v1alpha3 kind: ServiceEntry metadata: name: httpbin-ext spec: hosts:

    • httpbin.org ports:
    • number: 80 name: http protocol: HTTP resolution: DNS location: MESH_EXTERNAL EOF {{< /text >}}

  2. Make a request to the external HTTP service from SOURCE_POD:

    {{< text bash >}} $ kubectl exec -it $SOURCE_POD -c sleep -- curl http://httpbin.org/headers { "headers": { "Accept": "/", "Connection": "close", "Host": "httpbin.org", "User-Agent": "curl/7.60.0", ... "X-Envoy-Decorator-Operation": "httpbin.org:80/*", } } {{< /text >}}

    Note the headers added by the Istio sidecar proxy: X-Envoy-Decorator-Operation.

  3. Check the log of the sidecar proxy of SOURCE_POD:

    {{< text bash >}} $ kubectl logs $SOURCE_POD -c istio-proxy | tail [2019-01-24T12:17:11.640Z] "GET /headers HTTP/1.1" 200 - 0 599 214 214 "-" "curl/7.60.0" "17fde8f7-fa62-9b39-8999-302324e6def2" "httpbin.org" "35.173.6.94:80" outbound|80||httpbin.org - 35.173.6.94:80 172.30.109.82:55314 - {{< /text >}}

    Note the entry related to your HTTP request to httpbin.org/headers.

  4. Check the Mixer log. If Istio is deployed in the istio-system namespace, the command to print the log is:

    {{< text bash >}} $ kubectl -n istio-system logs -l istio-mixer-type=telemetry -c mixer | grep 'httpbin.org' {"level":"info","time":"2019-01-24T12:17:11.855496Z","instance":"accesslog.logentry.istio-system","apiClaims":"","apiKey":"","clientTraceId":"","connection_security_policy":"unknown","destinationApp":"","destinationIp":"I60GXg==","destinationName":"unknown","destinationNamespace":"default","destinationOwner":"unknown","destinationPrincipal":"","destinationServiceHost":"httpbin.org","destinationWorkload":"unknown","grpcMessage":"","grpcStatus":"","httpAuthority":"httpbin.org","latency":"214.661667ms","method":"GET","permissiveResponseCode":"none","permissiveResponsePolicyID":"none","protocol":"http","receivedBytes":270,"referer":"","reporter":"source","requestId":"17fde8f7-fa62-9b39-8999-302324e6def2","requestSize":0,"requestedServerName":"","responseCode":200,"responseSize":599,"responseTimestamp":"2019-01-24T12:17:11.855521Z","sentBytes":806,"sourceApp":"sleep","sourceIp":"AAAAAAAAAAAAAP//rB5tUg==","sourceName":"sleep-88ddbcfdd-rgk77","sourceNamespace":"default","sourceOwner":"kubernetes://apis/apps/v1/namespaces/default/deployments/sleep","sourcePrincipal":"","sourceWorkload":"sleep","url":"/headers","userAgent":"curl/7.60.0","xForwardedFor":"0.0.0.0"} {{< /text >}}

    Note that the destinationServiceHost attribute is equal to httpbin.org. Also notice the HTTP-related attributes: method, url, responseCode and others. Using Istio egress traffic control, you can monitor access to external HTTP services, including the HTTP-related information of each access.

Access an external HTTPS service

  1. Create a ServiceEntry to allow access to an external HTTPS service.

    {{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: networking.istio.io/v1alpha3 kind: ServiceEntry metadata: name: google spec: hosts:

    • www.google.com ports:
    • number: 443 name: https protocol: HTTPS resolution: DNS location: MESH_EXTERNAL EOF {{< /text >}}

  2. Make a request to the external HTTPS service from SOURCE_POD:

    {{< text bash >}} $ kubectl exec -it $SOURCE_POD -c sleep -- curl https://www.google.com | grep -o ""

    {{< /text >}}

  3. Check the log of the sidecar proxy of SOURCE_POD:

    {{< text bash >}} $ kubectl logs $SOURCE_POD -c istio-proxy | tail [2019-01-24T12:48:54.977Z] "- - -" 0 - 601 17766 1289 - "-" "-" "-" "-" "172.217.161.36:443" outbound|443||www.google.com 172.30.109.82:59480 172.217.161.36:443 172.30.109.82:59478 www.google.com {{< /text >}}

    Note the entry related to your HTTPS request to www.google.com.

  4. Check the Mixer log. If Istio is deployed in the istio-system namespace, the command to print the log is:

    {{< text bash >}} $ kubectl -n istio-system logs -l istio-mixer-type=telemetry -c mixer | grep 'www.google.com' {"level":"info","time":"2019-01-24T12:48:56.266553Z","instance":"tcpaccesslog.logentry.istio-system","connectionDuration":"1.289085134s","connectionEvent":"close","connection_security_policy":"unknown","destinationApp":"","destinationIp":"rNmhJA==","destinationName":"unknown","destinationNamespace":"default","destinationOwner":"unknown","destinationPrincipal":"","destinationServiceHost":"www.google.com","destinationWorkload":"unknown","protocol":"tcp","receivedBytes":601,"reporter":"source","requestedServerName":"www.google.com","sentBytes":17766,"sourceApp":"sleep","sourceIp":"rB5tUg==","sourceName":"sleep-88ddbcfdd-rgk77","sourceNamespace":"default","sourceOwner":"kubernetes://apis/apps/v1/namespaces/default/deployments/sleep","sourcePrincipal":"","sourceWorkload":"sleep","totalReceivedBytes":601,"totalSentBytes":17766} {{< /text >}}

    Note that the requestedServerName attribute is equal to www.google.com. Using Istio egress traffic control, you can monitor access to external HTTPS services, in particular the SNI and the number of sent and received bytes. Note that in HTTPS all the HTTP-related information like method, URL path, response code, is encrypted so Istio cannot see and cannot monitor that information for HTTPS. If you need to monitor HTTP-related information in access to external HTTPS services, you may want to let your applications issue HTTP requests and configure Istio to perform TLS origination.

Manage traffic to external services

Similar to inter-cluster requests, Istio routing rules can also be set for external services that are accessed using ServiceEntry configurations. In this example, you set a timeout rule on calls to the httpbin.org service.

  1. From inside the pod being used as the test source, make a curl request to the /delay endpoint of the httpbin.org external service:

    {{< text bash >}} $ kubectl exec -it $SOURCE_POD -c sleep sh $ time curl -o /dev/null -s -w "%{http_code}\n" http://httpbin.org/delay/5 200

    real 0m5.024s user 0m0.003s sys 0m0.003s {{< /text >}}

    The request should return 200 (OK) in approximately 5 seconds.

  2. Exit the source pod and use kubectl to set a 3s timeout on calls to the httpbin.org external service:

    {{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: networking.istio.io/v1alpha3 kind: VirtualService metadata: name: httpbin-ext spec: hosts: - httpbin.org http:

    • timeout: 3s route:
      • destination: host: httpbin.org weight: 100 EOF {{< /text >}}

  3. Wait a few seconds, then make the curl request again:

    {{< text bash >}} $ kubectl exec -it $SOURCE_POD -c sleep sh $ time curl -o /dev/null -s -w "%{http_code}\n" http://httpbin.org/delay/5 504

    real 0m3.149s user 0m0.004s sys 0m0.004s {{< /text >}}

    This time a 504 (Gateway Timeout) appears after 3 seconds. Although httpbin.org was waiting 5 seconds, Istio cut off the request at 3 seconds.

Cleanup the controlled access to external services

{{< text bash >}} $ kubectl delete serviceentry httpbin-ext google $ kubectl delete virtualservice httpbin-ext --ignore-not-found=true {{< /text >}}

Direct access to external services

If you want to completely bypass Istio for a specific IP range, you can configure the Envoy sidecars to prevent them from intercepting the external requests. This can be done by setting the global.proxy.includeIPRanges variable of Helm and updating the istio-sidecar-injector configmap by using kubectl apply. After istio-sidecar-injector is updated, the value of global.proxy.includeIPRanges will affect all the future deployments of the application pods.

The simplest way to use the global.proxy.includeIPRanges variable is to pass it the IP range(s) used for internal cluster services, thereby excluding external IPs from being redirected to the sidecar proxy. The values used for internal IP range(s), however, depends on where your cluster is running. For example, with Minikube the range is 10.0.0.1/24, so you would update your istio-sidecar-injector configmap like this:

{{< text bash >}} $ helm template install/kubernetes/helm/istio --set global.proxy.includeIPRanges="10.0.0.1/24" -x templates/sidecar-injector-configmap.yaml | kubectl apply -f - {{< /text >}}

Note that you should use the same Helm command you used to install Istio, in particular, the same value of the --namespace flag. In addition to the flags you used to install Istio, add --set global.proxy.includeIPRanges="10.0.0.1/24" -x templates/sidecar-injector-configmap.yaml.

Redeploy the sleep application as described in the Before you begin section.

{{< warning >}} Make sure to remove the previously deployed ServiceEntry and VirtualService. {{< /warning >}}

Set the value of global.proxy.includeIPRanges

Set the value of global.proxy.includeIPRanges according to your cluster provider.

IBM Cloud Private

  1. Get your service_cluster_ip_range from IBM Cloud Private configuration file under cluster/config.yaml:

    {{< text bash >}} $ cat cluster/config.yaml | grep service_cluster_ip_range {{< /text >}}

    The following is a sample output:

    {{< text plain >}} service_cluster_ip_range: 10.0.0.1/24 {{< /text >}}

  2. Use --set global.proxy.includeIPRanges="10.0.0.1/24"

IBM Cloud Kubernetes Service

Use --set global.proxy.includeIPRanges="172.30.0.0/16\,172.21.0.0/16\,10.10.10.0/24"

Google Container Engine (GKE)

The ranges are not fixed, so you will need to run the gcloud container clusters describe command to determine the ranges to use. For example:

{{< text bash >}} $ gcloud container clusters describe XXXXXXX --zone=XXXXXX | grep -e clusterIpv4Cidr -e servicesIpv4Cidr clusterIpv4Cidr: 10.4.0.0/14 servicesIpv4Cidr: 10.7.240.0/20 {{< /text >}}

Use --set global.proxy.includeIPRanges="10.4.0.0/14\,10.7.240.0/20"

Azure Container Service(ACS)

Use --set global.proxy.includeIPRanges="10.244.0.0/16\,10.240.0.0/16

Minikube, Docker For Desktop, Bare Metal

The default value is 10.96.0.0/12, but it's not fixed. Use the following command to determine your actual value:

{{< text bash >}} $ kubectl describe pod kube-apiserver -n kube-system | grep 'service-cluster-ip-range' --service-cluster-ip-range=10.96.0.0/12 {{< /text >}}

Use --set global.proxy.includeIPRanges="10.96.0.0/12"

Access the external services

After updating the istio-sidecar-injector configmap and redeploying the sleep application, the Istio sidecar will only intercept and manage internal requests within the cluster. Any external request bypasses the sidecar and goes straight to its intended destination. For example:

{{< text bash >}} export SOURCE_POD=(kubectl get pod -l app=sleep -o jsonpath={.items..metadata.name}) $ kubectl exec -it $SOURCE_POD -c sleep curl http://httpbin.org/headers { "headers": { "Accept": "/", "Connection": "close", "Host": "httpbin.org", "User-Agent": "curl/7.60.0" } } {{< /text >}}

Unlike accessing external services through HTTP or HTTPS, you don't see any headers related to the Istio sidecar and the requests sent to external services appear neither in the log of the sidecar nor in the Mixer log. Bypassing the Istio sidecars means you can no longer monitor the access to external services.

Cleanup the direct access to external services

Update the istio-sidecar-injector.configmap.yaml configuration map to redirect all outbound traffic to the sidecar proxies:

{{< text bash >}} $ helm template install/kubernetes/helm/istio -x templates/sidecar-injector-configmap.yaml | kubectl apply -f - {{< /text >}}

Install Istio with access to all external services by default

An alternative to calling external services directly is to instruct the Istio proxy to pass through, instead of block, calls to external services by default. This option allows you to start evaluating Istio quickly, without controlling access to external services, and decide to configure access to external services later.

Istio has an installation option that allows access to any external service on any ports without an HTTP service or a service entry within the mesh. For example, if you don't register an HTTP service or define a service entry for port 8000 within the mesh, you can configure the sidecar proxy to pass the request to any external service on that port. If you later create an HTTP service inside the mesh on port 8000 or define a service entry for any host on port 8000, Istio will block all external access to port 8000 since Istio then falls back to the blocking-by-default behavior for that port.

{{< warning >}} Some ports, for example port 80, have HTTP services inside Istio by default. Because of this caveat, you cannot use this approach for services using those ports. {{< /warning >}}

  1. To allow access to all the external services, install or update Istio by using Helm while setting the value of global.outboundTrafficPolicy.mode to ALLOW_ANY: --set global.outboundTrafficPolicy.mode=ALLOW_ANY.

    Alternatively, if you followed the instructions in Quick Start with Kubernetes and used install/kubernetes/istio-demo.yaml or install/kubernetes/istio-demo-auth.yaml files to install Istio, just edit the files. Look for the following YAML part:

    {{< text yaml >}}

    Set the default behavior of the sidecar for handling outbound traffic from the application:

    REGISTRY_ONLY - restrict outbound traffic to services defined in the service registry as well

    as those defined through ServiceEntries

    ALLOW_ANY - outbound traffic to unknown destinations will be allowed, in case there are no

    services or ServiceEntries for the destination port

    outboundTrafficPolicy: mode: REGISTRY_ONLY {{< /text >}}

    Change mode of outboundTrafficPolicy from REGISTRY_ONLY to ALLOW_ANY. Then run kubectl apply with the edited file.

    Yet another option is to use kubectl edit to edit the relevant configuration map directly: kubectl edit configmap istio -n istio-system.

    For demonstration purposes, let's use kubectl get --export, kubectl replace and sed:

    {{< text bash >}} $ kubectl get configmap istio -n istio-system --export -o yaml | sed 's/mode: REGISTRY_ONLY/mode: ALLOW_ANY/g' | kubectl replace -n istio-system -f - configmap "istio" replaced {{< /text >}}

  2. Make a couple of requests to external HTTPS services from SOURCE_POD:

    {{< text bash >}} $ kubectl exec -it $SOURCE_POD -c sleep -- curl -s https://www.google.com | grep -o ""; kubectl exec -it $SOURCE_POD -c sleep -- curl -s https://edition.cnn.com | grep -o ""

    {{< /text >}}

    {{< warning >}} It might take time for the configuration change to propagate so you might still get connection errors. Wait for several seconds and then retry the last command. {{< /warning >}}

Note that the requests to port 80 are blocked for all the external services since Istio by default has HTTP services that run on port 80. Also note that if you install Istio with allowed access to all the external services you loose Istio monitoring on traffic to external services: the calls to external services will not appear in the Mixer log, for example. To start monitoring access to external services, follow the steps in configure access to external services (no need to update Istio).

Change back to the blocking-by-default policy

To cancel your policy change for external services, undo the changes you performed in the previous section and update Istio.

  1. For demonstration purposes, run:

    {{< text bash >}} $ kubectl get configmap istio -n istio-system --export -o yaml | sed 's/mode: ALLOW_ANY/mode: REGISTRY_ONLY/g' | kubectl replace -n istio-system -f - configmap "istio" replaced {{< /text >}}

  2. Make a couple of requests to external HTTPS services from SOURCE_POD to verify that they are now blocked:

    {{< text bash >}} $ kubectl exec -it $SOURCE_POD -c sleep -- curl -s https://www.google.com | grep -o ""; kubectl exec -it $SOURCE_POD -c sleep -- curl -s https://edition.cnn.com | grep -o "" command terminated with exit code 35 command terminated with exit code 35 {{< /text >}}

    {{< warning >}} It might take time for the configuration change to propagate so you might still get successful connections. Wait for several seconds and then retry the last command. {{< /warning >}}

Understanding what happened

In this task you looked at three ways to call external services from an Istio mesh:

  1. Use a service entry to register an accessible external service inside the mesh. This is the recommended approach.

  2. Configuring the Istio sidecar to exclude external IPs from its remapped IP table.

  3. Configuring Istio to allow access to any external service on some ports.

The first approach lets you use all of the same Istio service mesh features for calls to services inside or outside of the cluster. You saw how to monitor access to external services and set a timeout rule for calls to an external service.

The second approach bypasses the Istio sidecar proxy, giving your services direct access to any external server. However, configuring the proxy this way does require cluster-provider specific knowledge and configuration. Additionally, you lose monitoring of access to external services and you can't apply Istio features on traffic to external services.

The third approach directs traffic through the Istio sidecar proxy but it allows access to any service on any port that has no HTTP service or service entry defined in the mesh. Similar to the second approach, you can't monitor access to external services but you don't need to know which IP ranges are external to the cluster. You can easily switch to the first approach for a specific port by simply creating a service entry for that port. This means you can use this approach initially to allow access to any external service. Later, you can decide to start controlling access to external services for specific ports and enable traffic monitoring and control features as they are needed.

Security note

{{< warning >}} Note that configuration examples in this task do not enable secure egress traffic control in Istio. A malicious application can bypass the Istio sidecar proxy and access any external service without Istio control. {{< /warning >}}

To implement egress traffic control in a secure way, you must direct egress traffic through an egress gateway and address the security concerns expressed in Configure an Egress Gateway example, Additional Security Considerations.

Cleanup

Shutdown the [sleep]({{< github_tree >}}/samples/sleep) service:

{{< text bash >}} $ kubectl delete -f @samples/sleep/sleep.yaml@ {{< /text >}}